A premix burner is disclosed with a swirl generator which delimits a conical swirl space and provides at least two conical part shells which are arranged, offset to one another, along a burner axis, mutually enclose in each case air inlet slits running longitudinally with respect to the burner axis and have in combination a conically widening premix burner outer contour having a maximum outside diameter which narrows axially into a region with a minimum outside diameter.
Premix burners of the generic type mentioned above are known from a multiplicity of publications with prior priority dates, such as, for example, from EP A1 0 210 462 and EP B1 0 321 809, to name only a few. Premix burners of this type are based on a general operative principle whereby, within a mostly conically designed swirl generator which provides at least two conical part shells assembled with a corresponding mutual overlap, a swirl flow is generated which consists of a fuel/air mixture and which is ignited within a combustion chamber following the premix burner in the flow direction, so as to form a premix flame which is as stable as possible in spatial terms.
Whether in a single or a multiple arrangement, premix burners of this type are used for the firing of combustion chambers in order to operate a thermal engine, in particular in gas or steam turbine plants, especially since these premix burners make it possible to use different fuels for forming a largely homogeneous fuel/air mixture which can ultimately be ignited so as to form an aerodynamically stabilized premix flame.
The operation of thermal power plants, in particular of gas turbine plants, has to satisfy high requirements in terms of their environmental compatibility, while the exhaust gases released into the atmosphere as a result of the combustion process are subject to strict emission limit values. Moreover, thermal power plants are to be optimized from the standpoint of their efficiency with which they are capable of converting energy into electrical energy, this applying as far as possible over the entire spectrum of their power range.
Present gas turbine plants are operated in a way known per se according to a permanently predetermined operating pattern which depends on a limited number of individually predetermined ambient conditions. Thus, such ambient conditions are, for example, the ambient temperature, the air humidity and also fuel qualities, to name only a few. The operating behavior of a gas turbine plant is influenced appreciably by these external influences. Thus, taking into account these and other ambient conditions, before the gas turbine plant, for example a predetermined construction series, is commissioned, what is known as an operating manual or “operating schedule” is drawn up, according to which important controlled variables are fixed which are to ensure as optimized an operation of the gas turbine plant as possible over the entire load range. The controlled variables relate particularly to quantitative and qualitative variables which regulate the supply of fuel and of combustion air to the burner unit.
Problems may arise, however, insofar as even the slightest manufacturing deviations are to be observed within a gas turbine series which relate particularly to the burner component. Since the premix burner of the type initially mentioned which is used in the burner has an optimized form of construction in terms of flame stability and emission behavior, even the slightest deviations in the premix burner design which impair the aerodynamic flow may have considerably adverse effects on the combustion result. If the combustion process is conducted in a way known per se by means of permanently predetermined controlled variables which cannot take into account the design deviations possibly occurring as a consequence of manufacture, this can lead to an unsatisfactory combustion result, which is ultimately reflected in the occurrence of overheatings in the burner or in the hot gas path lying downstream of the burner, in thermoacoustic oscillations, as they are known, and in impaired emission values. System-related aging phenomena in the individual components of the gas turbines can also contribute to impairing the operating behavior of the overall gas turbine plant as the age of the plant increases.